/*
 *  Licensed to the Apache Software Foundation (ASF) under one
 *  or more contributor license agreements.  See the NOTICE file
 *  distributed with this work for additional information
 *  regarding copyright ownership.  The ASF licenses this file
 *  to you under the Apache License, Version 2.0 (the
 *  "License"); you may not use this file except in compliance
 *  with the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing,
 *  software distributed under the License is distributed on an
 *  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 *  KIND, either express or implied.  See the License for the
 *  specific language governing permissions and limitations
 *  under the License.
 *
 */
package lex.fsm;

/**
 * The interface implemented by classes which need to react on transitions
 * between states.
 * 
 * @author The Apache MINA Project (dev@mina.apache.org)
 * @version $Rev: 586695 $, $Date: 2010/01/30 15:30:00 $
 */
public interface Transition {
	/**
	 * Executes this {@link Transition}. It is the responsibility of this
	 * {@link Transition} to determine whether it actually applies for the
	 * specified {@link StateEvent}. If this {@link Transition} doesn't apply
	 * nothing should be executed and <code>false</code> must be returned.
	 * 
	 * @param event
	 *            the current {@link StateEvent}.
	 * @return <code>true</code> if the {@link Transition} was executed,
	 *         <code>false</code> otherwise.
	 */
	boolean accept(StateEvent event);

	/**
	 * Returns the {@link State} which the {@link StateMachine} should move to
	 * if this {@link Transition} is taken and {@link #accept(StateEvent)}
	 * returns <code>true</code>.
	 * 
	 * @return the next {@link State} or <code>null</code> if this
	 *         {@link Transition} is a loopback {@link Transition}.
	 */
	State getNextState();
}
